Resistivity of Solid and Liquid Fe-Ni-Si with applications to the cores of Earth, Mercury and Venus
Electrical resistivity measurements of Fe-10wt%Ni-10wt%Si have been performed in a multi-anvil press from 3-20 GPa up to 2200 K. The temperature and pressure dependences of electrical resistivity are analyzed in term of changes in the electron mean free path. Similarities in the thermal properties of Fe-Si and Fe-Ni-Si alloys suggest the effect of Ni is negligible. Electrical resistivity is used to calculate thermal conductivity via the Wiedemann-Franz law, which is then used to estimate the adiabatic heat flow. The adiabatic heat flow at the top of Earth’s core is estimated to be 14 TW from the pressure and temperature dependences of thermal conductivity in the liquid state from this study, more than twice that of a pure Fe core. The calculated adiabatic heat flux density of 22.7-32.1 mW/m2 at the top of Mercury’s core suggests a chemically driven magnetic field from 0.02-0.21 Gyr after formation. A thermal conductivity of 140-148 Wm−1K−1 is estimated at the center of a Fe-10wt%Ni-10wt%Si Venusian core, suggesting the presence of a solid inner core and an outer core that is at least partially liquid.